The subject matter disclosed herein relates to fuel heating system using hot and warm water sources.
In general, gas turbine engines include a compressor, a combustor, and a turbine. The compressor and turbine generally include rows of blades that are axially stacked in stages. Each stage includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central axis or shaft. In operation, the compressor rotor blades rotate about the shaft, and, acting in concert with the stator blades, compress a flow of air. The supply of compressed air then is used in the combustor to combust a supply of fuel. The resulting flow of hot gases from the combustion is expanded through the turbine and causes the turbine blades to rotate such that the system as a whole acts to convert fuel into mechanical energy.
Often, the supply of fuel used in a combustor is preheated to promote efficient engine operation. As such, it is occasionally necessary to vary the preheated temperature of the fuel based on changing fuel characteristics. However, a conventional fuel delivery system may have limitations that result in difficulties or delays in controlling the preheated temperature of fuel as it is delivered to the combustor. This may lead to the fuel being delivered at inappropriate preheated temperatures.
Combustion turbine engines are generally designed to operate using fuels having certain characteristics relating to heating value. The heating value of a fuel, which also may be referred to as the gross calorific heating value of the fuel, gross energy or wobbe index rating, generally describes the amount of heat or energy released when the fuel is combusted. In combustion turbine engine applications, though, the amount of energy released by a fuel being combusted through a fuel nozzle at a given pressure ratio may be more accurately described if the temperature at which the fuel is delivered to the nozzle is taken into account. The fuel characteristic that takes into account or compensates for the temperature of the fuel is generally referred to as the modified wobbe index (MWI) rating, which is equal to the Lower Heating Value (LHV) of the fuel divided by the square root of the absolute temperature of the fuel times the specific gravity of the fuel. The MWI rating thus refers to a fuel measure describing the amount of energy released by a fuel being combusted through a fuel nozzle at a given pressure ratio that takes into account or compensates for the temperature at which the fuel is delivered to the nozzle.
Combustion turbine engines are generally designed to operate with fuels that have a specific MWI rating or fall within a range of acceptable MWI ratings. This being the case, having the capability to modify or control the temperature of the fuel being delivered to the combustor (thereby modifying or controlling the MWI rating of the fuel) is a useful way to insure the engine is using acceptable fuel that promotes efficient operation and reduces the risk of combustor damage.
However, given limitations of conventional systems, different fuels of differing compositions and heating values may be successively delivered to the combustor with conditions lying outside of the acceptable or targeted MWI rating. This may subsequently result in damage to the combustor, inefficient engine performance and/or downgraded engine operation.